Many conditions benefit from shunting, removal, or cleansing of CSF, including hydrocephalus, pseudotumor cerebri (Idiopathic Intracranial Hypertension, IIH), and Alzheimer's disease. Hydrocephalus, for example, is a condition afflicting patients who are unable to regulate cerebrospinal fluid flow through their body's own natural pathways. Produced by the ventricular system, cerebrospinal fluid (CSF) is normally absorbed by the body's venous system. In a patient suffering from hydrocephalus, the cerebrospinal fluid is not absorbed in this manner, but instead accumulates in the ventricles of the patient's brain and can lead to serious medical conditions.
Hydrocephalus exists in two forms: communicating (non-obstructive hydrocephalus) caused by inadequate absorption of CSF when the ventricular pathways are not obstructed; and non-communicating (obstructive hydrocephalus) caused by blockage in the ventricular pathways through which CSF flows. Hydrocephalus can also be either congenital, where the condition is present at birth or detected soon thereafter, or acquired, where the condition is acquired as the result of infection, head trauma, brain tumors, cysts, etc. Normal pressure hydrocephalus (NPH) is a type of communicating (non-obstructive) hydrocephalous that occurs in adults, usually older adults. The drainage of CSF is blocked gradually, and the excess fluid builds up slowly. With NPH it is believed that the ventricles enlarge to handle the increased volume of the CSF, and the compression of the brain from within by the fluid-filled ventricles destroys or damages brain tissue causing some of the symptoms. Unlike other types of Hydrocephalus that typically result in increased pressure in the head when too much CSF accumulates, NPH shows little to no increased pressure, thus leading to the name “Normal Pressure Hydrocephalus.”
NPH can be treated by draining the excess fluid from the ventricular system to another area of the patient's body, such as the abdomen or vascular system, where it can be reabsorbed into the bloodstream. A drainage system, commonly referred to as a shunt, is often used to carry out the transfer of fluid. It consists of a system of catheters with a flow control component to control fluid drainage and prevent back-flow. In order to install the shunt, typically a scalp incision is made and a small hole is drilled in the skull. Current shunts used to treat NPH are inserted surgically so that the upper end is in communication with the ventricular system. Since NPH is non-obstructive, the upper end or proximal catheter of the shunt can be placed either in the ventricles (ventricular catheter) or in the sub-arachnoid space at the level of the lumbar spinal column (lumbar catheter). The lower end or distal catheter of the shunt can lead into the abdomen (ventriculo-peritoneal shunt), wherein it passes into the bloodstream. There are several other body cavities available for distal drainage of a shunt. When shunts were first introduced, a one-way valve drained spinal fluid directly into the right atrium of the heart via the jugular vein (ventriculoatrial shunt). Vascular shunts functioned very well, but they were prone to multiple problems including early and late infection, as well as rare, potentially fatal heart failure due to blockage of blood vessels within the lungs by particles of blood clot flaking off the shunt's catheter tip. The use of the heart has been largely abandoned as an initial choice because of these problems but it remains a viable second option when infection or surgery has rendered the abdominal cavity unaccommodating of the distal shunt catheter. The chest cavity is another cavity which can be used as a backup to the abdominal cavity (ventriculopleural shunt). The catheter is placed inside the rib cage between its inner lining and the outer lining of the lungs. Occasionally, this cavity cannot resorb the CSF rapidly and the lung becomes compressed by the excess CSF resulting in difficulty in breathing. The catheter must be moved to a different cavity is such cases. Rarely, the catheter can rest on the diaphragm (the muscle at the base of the lungs used for breathing), causing irritation and hiccups.
While shunts were a major medical breakthrough, there are problems that still remain unsolved in the treatment of hydrocephalus, including shunt obstruction, infection, and overdrainage. Shunted NPH only has a success rate of about 50%. These same problems also exist with other conditions which are treated by CSF diversion, such as pseudotumor cerebri.
Accordingly, there remains a need for improved methods and devices for draining CSF to treat hydrocephalous, pseudotumor cerebri (IIH), or any other condition in which it is necessary to drain and/or cleanse CSF, potentially including Alzheimer's Disease.